Fecal Coliform Removal In Algal-Based Domestic Wastewater Treatment Systems

We hypothesize that the net effect of organic matter (from all sources) in domestic wastewater treatment ponds may tend to promote fecal bacteria survival at higher algal cell concentrations. The aim of this study is to understand better, the role of algae in the removal of fecal bacteria from algal based ponds and to specifically investigate the effect of varying algal concentrations on fecal bacteria removal in algal based ponds. Batch laboratory experiments were conducted using light of wavelengths, 380-780 nm. Algae were grown by natural colonization and used for inoculating the setup

A 3-step strategic approach to sustainable wastewater managementage/gi

Many cities in developing countries are facing surface water and groundwater pollution problems. This deterioration of water resources needs to be controlled through effective and feasible concepts of urban water management. The Dublin Principles, Agenda21, Vision21, and the Millennium Development Goals provide the basis for the development of innovative, holistic, and sustainable approaches. Whilst highly efficient technologies are available, the infusion of these into a well-thought out and systematic approach is critical for the sustainable management of nutrient flows and other pollutants into and out of cities. Based on cleaner production principles, three intervention steps are proposed in this paper. The first step is to minimise wastewater generation by drastically reducing water consumption and waste generation. The second step is the treatment and optimal reuse of nutrients and water at the smallest possible level, like at the on-plot and community levels. Treatment technologies recommended make the best use of side products via reuse. Once the first two intervention steps have been employed to the maximum, the remaining waste flows could be safely discharged into the environment. The third step involves enhancing the self-purification capacity of receiving water-bodies (lakes, rivers, etc.), through intervention. The success of this so-called 3-step strategic approach requires systematic implementation, providing specific solutions to specific situations. This, in turn, requires appropriate planning, legal and institutional responses. In fact, the 3-step approach could be applied as an overall approach for waste management, although here the focus is on sewage. This paper offers examples under each step, showing that the systematic application of this approach could lead to cost savings and sustainability. Key words: cleaner production, nutrients reuse, 3-step strategic approach, sustainable approaches, urban water cycle, wastewater management Water SA Vol.31(1) 2005: 133-14

Sustainable decentralized sanitation using duckweed-based ponds

This paper focuses on the performance and operational problems at two full-scale duckweed-based systems in the Masvingo province of Zimbabwe

Optimizing irrigation water use in the West Bank, Palestine

We examine optimal irrigation water allocation on the West Bank using a linear mathematical programming model. Our analysis involves five agricultural zones and five fruit and vegetable crops: tomatoes, cucumbers, eggplant, squash and citrus. We analyze three scenarios: (1) maintaining the existing cropping patterns, (2) maximizing profit under water and land availability constraints, and (3) maximizing profit under water and land availability constraints, while also imposing an additional constraint requiring production of crops for local consumption. The water used for irrigation is reduced by 10% (4% of all agricultural water use) by changing the cropping patterns of the five crops we analyze under land and water availability constraints. The total value added in irrigated agriculture increases by 38%, equivalent to 4% of the entire agricultural sector. Imposing the additional constraint requiring production for local consumption also reduces irrigation water use by 10%, while the increase in value added is only 12% (1% for the entire agricultural sector).Agriculture Cropping patterns Linear programming Profit maximization Water scarcity

Modeling the PAO–GAO competition: Effects of carbon source, pH and temperature

The influence of different carbon sources (acetate to propionate ratios), temperature and pH levels on the competition between polyphosphate- and glycogen-accumulating organisms (PAO and GAO, respectively) was evaluated using a metabolic model that incorporated the carbon source, temperature and pH dependences of these microorganisms. The model satisfactorily described the bacterial activity of PAO (Accumulibacter) and GAO (Competibacter and Alphaproteobacteria-GAO) laboratory-enriched cultures cultivated on propionate (HPr) and acetate (HAc) at standard conditions (20 °C and pH 7.0). Using the calibrated model, the effects of different influent HAc to HPr ratios (100–0, 75–25, 50–50 and 0–100%), temperatures (10, 20 and 30 °C) and pH levels (6.0, 7.0 and 7.5) on the competition among Accumulibacter, Competibacter and Alphaproteobacteria-GAO were evaluated. The main aim was to assess which conditions were favorable for the existence of PAO and, therefore, beneficial for the biological phosphorus removal process in sewage treatment plants. At low temperature (10 °C), PAO were the dominant microorganisms regardless of the used influent carbon source or pH. At moderate temperature (20 °C), PAO dominated the competition when HAc and HPr were simultaneously supplied (75–25 and 50–50% HAc to HPr ratios). However, the use of either HAc or HPr as sole carbon source at 20 °C was not favorable for PAO unless a high pH was used (7.5). Meanwhile, at higher temperature (30 °C), GAO tended to be the dominant microorganisms. Nevertheless, the combined presence of acetate and propionate in the influent (75–25 and 50–50% HAc to HPr ratios) as well as a high pH (7.5) appear to be potential factors to favor the metabolism of PAO over GAO at higher sewage temperature (30 °C)

A Financial, Environmental and Social Evaluation of Domestic Water Management Options in the West Bank, Palestine

Water is one of the most valuable natural resources in the West Bank, Palestine. Due to its limited availability, it is a resource that needs particular protection. Although agriculture consumes most of the water (70%) in the West Bank, the domestic water supply is strategically not less important. It is the aim of this study to evaluate domestic water management options suitable for Palestinian conditions that contribute to achieving water sufficiency in the domestic water use in the house of tomorrow. A number of options were evaluated economically, environmentally and socially using the concept of life cycle impact assessment (LCIA). Results of the study showed that by introducing a combination of domestic water management options, a substantial decrease in the water consumption of more than 50% can be achieved, thereby reducing the pressure on the scarce water resources. The annual environmental impact of the in-house water use can be reduced in the range of 8%, when using low-flow shower head to 38% when using rainwater harvesting systems. Some of the options (faucet aerators, low-flow shower heads and dual flush toilets) were found to be financially attractive with a pay back period of less than their expected lives, others (rainwater harvesting, graywater reuse and dry toilets) were found to be financially unattractive because of the high investment. In the social context, it was found that introducing such options can improve the quality of life of those not having enough water. There is already a popular willingness to take part in water conservation in the domestic sector in the West Bank. The strongest driving force for using water conservation measures is the awareness that water is a scarce resource. It was concluded that, theoretically, the house of tomorrow can be largely independent in terms of water and sanitation. Education and awareness campaigns in the context of water management with a focus on non-traditional options are key to achieve such a house.Water ManagementCivil Engineering and Geoscience